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Reference Manual
00809-0400-4728, Rev AA
June 2011
Rosemount 644
A-4
FOUNDATION FIELDBUS
SPECIFICATIONS
Function Blocks
Resource Block
• The resource block contains physical transmitter information including
available memory, manufacture identification, device type, software tag,
and unique identification.
Transducer Block
• The transducer block contains the actual temperature measurement data,
including sensor 1 and terminal temperature. It includes information about
sensor type and configuration, engineering units, linearization, reranging,
damping, temperature correction, and diagnostics.
LCD Block
• The LCD block is used to configure the local display, if an LCD Display is
being used.
Analog Input (AI)
• Processes the measurement and makes it available on the fieldbus
segment.
• Allows filtering, alarming, and engineering unit changes.
PID Block
• The transmitter provides control functionality with one PID function block in
the transmitter. The PID block can be used to perform single loop,
cascade, or feedforward control in the field.
Instantiable Function Blocks
• All the function blocks used by the transmitter are instantiable, meaning
the total number of function blocks is only limited by the physical memory
available in the transmitter. Since only the instantiable blocks can use
physical memory, any combination of function blocks can be used at any
given time as long as the physical memory size is not violated.
Rosemount Conformance to Specifications
A Rosemount product not only meets its published specifications, but most likely exceeds
them. Advanced manufacturing techniques and the use of Statistical Process Control provide
specification conformance to at least ± 3
(1)
. Our commitment to continual improvement
ensures that product design, reliability, and performance will improve annually.
For example, the Reference Accuracy distribution for the 644 is shown to the right. Our
Specification Limits are ± 0.15 °C, but, as the shaded area shows, approximately 68% of the
units perform three times better than the limits. Therefore, it is very likely that you will receive
a device that performs much better than our published specifications.
Conversely, a vendor who “grades” product without using Process Control, or who is not
committed to ± 3 performance, will ship a higher percentage of units that are barely within
advertised specification limits.
Accuracy distribution shown is for the 644, Pt
100 RTD sensor, Range 0 to 100 °C
(1) Sigma () is a statistical symbol to designate the standard deviation from the mean value of a normal distribution.
Lower
Specification
Limit
Upper
Specification
Limit
Typical Accuracy
3144-GRAPH
–3 –2 –1 1 2 3
Block Execution Time (milliseconds)
Resource –
Transducer –
LCD Block –
Analog Input 1 45
Analog Input 2 45
PID 1 60